Dispersant type Viscosity Index Improvers can be prepared by the modification of oil soluble polymers to provide functionality on the polymer which promotes dispersancy and detergency characteristics useful in preventing deposition of sludge and other deposits formed in the operation of gasoline or diesel engines. In the patent literature, a number of methods by which oil soluble hydrocarbon polymers may be modified to contain nitrogen and/or oxygen functionality are reported.
Other dispersant materials are prepared by sulfonation of polymers followed by neutralization. Some of the dispersant materials are polymer molecules having a multiplicity of sulfonate groups.
For example, U.S. Pat. No. 4,372,862 describes additives prepared by sulfonation of EPDM (ethylene propylene diene terpolymer) followed by neutralization with a variety of metal salts such as NaOH, KOH, LiOH, Mg(OH).sub.2. In U.S. Pat. No. 4,382,005, the preparation of sulfonated polymers wherein neutralization is performed using amines or ammonia is described. Other molecules, such as polyisobutylenes, can be sulfonated only once at most on each molecule.